Fixed decimal for Nav or Com Radio?

Hello,

I am using the opencockpit I/O card , opencockpit diplay card along with their 7 segment circuit board (holds five "7-segment displays") to try to get a nav or Com radio to work.In the early stages, every thing seems to be working correctly except for the fixed decimal place........... no decimal is showing?

I have posted on the Opencockpits forums, but have not got any answers yet.Does anybody here have any experience with this type of set up?



1. Can I use SIOC to get the decimal to work?

2. If not, do I need to short circuit the pin of the decimal some how ( without using a resistor?

3. Or , Do I need another 5 volt source ( and resistor) to feed power to the decimal.

Thanks,



Polmer

Hans mentioned this code using SIOC ( which address the decimal place issue).

I will give this a try.



Var 0015, Link IOCARD_DISPLAY, Digit 0, Numbers 5 // Active Frequency

Var 0017, Link IOCARD_OUT, Output 13 // actv hundreds Dec Pt

Var 0045, Link SUBRUTINE // Display the COM-1 active frequency
{
V0015 = FROMBCD V0994
V0015 = V0015 + 10000 // Show the number <== this is what you want to do!
V0017 = 1 // Show the decimal point
}
Var 0994, Link FSUIPC_IN, Offset $034E, Length 2 // actv COM-1 in
{
CALL V0045 // Disassemble and display this value
}




Polmer

The word on the street is to grab a 5 volt source ( via SIOC or other) and connect to the decimal using a 330 ohm capacitor.

ThanksNico.




Polmer

Ok.. If you are going to use a 330ohm resistor, would it not be just as easy to use 2.5 - 3.0 volt PS and not use the resistor? I am just asking...

LOL Bob,

In an ideal world yes, you could do that. However in the electronics world, we call this 330Ohm Resistor a current limiting resistor. It prevents many things, primarily it protects and limits output current from your interface card. Think of it in this analogy.

Can you run a car on just rims and no rubber?

The answer is yes however at very slow speeds, but there still is the possibility of spinning out

So you can run an LED on 2.5 to 3 volts without the resistor, however there is a possibility that you could damage your interface card or the LED. The use of the resistor limits the output of current from the interface card.

Hope that helps.

Oh By the way. It is against the Law to speed, but most of us do it anyway :)

Trev

Well I understand this if your interface card is supplying the power, but some of the interfaces do not supply the power. The power to my leds is not supplied by the Epic interface system. I am however using a computer PS so I need the 330ohm resistor.

In my case, I am using the opencockpits I/O card in which has power supplied to the 7 segments. But for some reason, no power is supplied to the 8th pin , which is the decimal, nor can it be software controlled via SIOC or there I/O software ( very basic).

I can either use a permanent 5 volt source and connect the decimal via a 330 resistor and not have control over it OR use the I/O control ( same one that you would use to control leds) and at least have the decimal activate whenever SIOC tells it too.

It just seemed odd to be to have to weld a resistor to the decimal when all of the other functions ( with the card) have vast capabilities. Oh well, nothing is perfect.

Polmer

Quote:

---

Originally Posted by Polmer

..., nor can it be software controlled via SIOC or there I/O software ( very basic).

---

?? It can be controlled via SIOC, your giving the answer yourself in your next sentence... Just connect the DP via a resistor to an Output of the Master Card and control that output via SIOC, see for instance Hans his code earlier in this thread.

The Display2 card of opencockpits indeed does not control the DP of a 7-segment display. I guess this was a design decion in order to save a wire? Another reason could be that multiplexing a DP would lead to a very weak DP. Even putting 5V via a resistor to the DP gives you a rather weak DP, that's why I take 220 ohm..

But again, like I told you in the OpenCockpits Forum, you can control the DP via SIOC, easy and flexible.

Nico

Quote:

---

Originally Posted by Trevor Hale

LOL Bob,

So you can run an LED on 2.5 to 3 volts without the resistor, however there is a possibility that you could damage your interface card or the LED.

---

I think you have put it mildly..., it will almost certainly damage your led.
Here is a nice site with some basics about Leds.

http://www.talkingelectronics.com/html/Page01.html

Never connect a led without a resistor...

Nico

Oh ya... Never and I mean never, connect 12v to an led.... Poof is putting it mildly!! hehehehe